The present invention relates to a method of and an apparatus for assembling an electronic component, such as a ladder-type filter, having a plurality of inner parts being held under pressure and stored in a case.
FIGS. 1 and 2 show a conventional four-element ladder-type filter. This filter comprises two series ceramic resonators 2 and 3, two parallel ceramic resonators 4 and 5, an input terminal plate 6, a ground terminal plate 7, an output terminal plate 8, an internal connection terminal plate 9 and a plate spring 10, which are stored in a box-type case 1. Outlines of these inner parts are substantially equivalent to each other. FIG. 3 is a circuit diagram showing the electrical connection thereof.
The input terminal plate 6 is provided on its one major surface with a protruding portion 6a which is in pressure contact with a central portion of the series resonator 2. The ground terminal plate 7 is provided on both its major surfaces with protruding portions 7a and 7b which are in pressure contact with central portions of the two parallel resonators 4 and 5 respectively. The output terminal plate 8 is provided on both its major surfaces with protruding portions 8a and 8b which are in pressure contact with central portions of the parallel resonator 5 and series resonator 3 respectively. The internal connection terminal plate 9 has a portion 9a which is inserted between the series resonator 2 and parallel resonator 4, a portion 9b which is arranged next to an outer major surface of the series resonator 3, and a coupling portion 9c which connects these portions 9a and 9b. Since the plate spring 10 is interposed between the portion 9b and an inner side surface of the case 1, the terminals 6-9 and the resonators 2-5 are in pressure contact with each other to be electrically connected.
A cover sheet 11 is inserted in an opening of the case 1, and a cavity which is defined by the cover sheet 11 and the opening is filled up with filler 12 such as resin, whereby the opening of the case 1 is sealed. Lead portions 6b, 7c and 8c of the input terminal 6, the ground terminal 7 and the output terminal 8 protrude from the opening of the case 1.
In the conventional ladder-type filter having the aforementioned structure, the resonators 2-5 utilizing surface-directional spreading vibration mode are merely in point contact with the terminals 6-9 at the central protruding portions 6a, 7a, 7b, 8a and 8b. Therefore, it is necessary to manually insert the resonators 2-5 and the terminals 6-9 into the case 1 one by one with tweezers since these parts easily get slanted due to the point contact. As a result, working efficiency of the assembling operation becomes quite low. Further, since it is necessary to bring all parts into close contact with each other in the final stage of assembly, much time is required for inserting the final part into a very small clearance. Moreover, electrode surfaces of the resonators 2-5 may be damaged by the assembling operation.
Thus, the conventional method of assembling electronic component such as a ladder-type filter had a problem of low working efficiency caused by manual assembly.